Process for the manufacture of a tire having a carcass reinforcement which is formed of at least one ply of cords or cables

ABSTRACT

A process for the manufacture of a tire which consists of producing a  toral carcass reinforcement blank (1) by the helical winding of a cord or cable around a non-deformable, annular building core N, followed by at least one circumferential cut on the radially inner surface of the core N and a cut on the radially outer surface, the two halves of the blank being then separated axially to permit the removal of the core and subsequently brought together and connected for the finishing of the blank of the tire.

The present invention relates to a process for the manufacture of a tirehaving at least one carcass reinforcement which is formed of plies ofcords or cables and, more particularly, a process for building thetoroidal blank of the tire.

The process most generally used in order to manufacture a tire for avehicle wheel consists essentially first of all in applying, one afterthe other around a cylindrical building drum, the different layers ofrubber mixes and the different plies of cords or cables which willconstitute the carcass reinforcement of the unvulcanized toroidal tireblank and of the tire itself; said carcass plies being in most casesanchored at each axial end of the drum to an annular metal reinforcementor bead wire.

In the case of a tire having a carcass reinforcement which is formed ofplies of bias cords or cables, the second step consists in applying tothe central zone of the unvulcanized cylindrical carcass blank the treadreinforcement plies, if any, or tread reinforcement plies, which areformed of cords or cables which are generally crossed from one ply tothe next. After the laying of said reinforcement, and the laying of thetread on the latter, the last step in the manufacture of the toroidalblank consists in imparting to it, before vulcanization, the shape of atorus which is very close to that of the finished tire. This operation,which is known as the shaping of the cylindrical blank, is carried outeither on a building drum or in the vulcanization mold itself.

In the case of a tire with radial carcass reinforcement, the second stepconsists in transforming the unvulcanized cylindrical carcass blank byshaping into an unvulcanized toroidal blank, and the last step thenconsists in placing on the central part of the toroidal blank a treadreinforcement, the layers of rubber mixes necessary and, in particular,the tread.

Despite the care taken in the carrying out of all of the operationsdescribed, despite the numerous verifications effected on the startingproducts, on the semi-finished products, and on the finished toroidalblank, and despite the numerous verifications on the manufacturingmachines and the manufacturing steps, the verifications effected on thefinished vulcanized tires show the presence of a number of abnormalitieswith respect to the position of the products, concerning in particularthe lower region, for which abnormalities no satisfactory explanationsare found. Furthermore, as is known, such processes require, beforetheir assembly, the separate manufacture of the plies of cords or cablesby means of large machines and with a large number of operations, andthey are therefore expensive.

In order to remedy the above-mentioned drawbacks, that is to say improvethe quality of the finished tire and decrease the cost of manufacture ofsaid tire, a new process for the manufacture of a tire is based, inaccordance with the present invention, on the principle that thesidewall regions and the bead regions of the blank must be built andhandled in the same geometrical configuration as that which they willhave in the vulcanization mold.

For the building of a carcass reinforcement, one can use the helicoidalwinding of a cord or cable on a foldable and/or disassemblable annularcore, followed by a cutting of the torus thus formed and removal of thetoroidal reinforcement blank from the building core. Such a manner ofmanufacture is described in U.S. Pat. No. 1,316,104.

U.S. Pat. No. 3,975,490 describes a method of manufacturing a tire intwo or three parts. If the tire is in three parts, two premoldedreinforced parts comprise the beads, the sidewalls and the reinforcedbands, support of the tread, the third part being the tread itself. Thispatent mentions the possibility of building the two reinforced parts bywinding rubberized woven strips around a toroidal core of circular crosssection and separating said blank into two sections by cuts. Enormousdifficulties are encountered in producing the reinforcements, inparticular of the reinforced bands by winding, in order to effect thecuts of the blank built in this manner and in order precisely to obtainreinforced bands which penetrate into each other after prevulcanization,in order to avoid displacements and deformations upon the handling ofthe sidewall parts of the tire.

The same is true in French Patent 1 214 908 in which the reinforcementis obtained by winding a layer of rubber mix on a disassemblablemandrel, followed by a layer of steel cables, the width measured betweenthe locations of the metal bead wires being approximately equal to twicethe width of each portion of ply necessary in order to be turned uparound the anchoring bead wires of the future carcass reinforcement.

German application 1 934 018 describes practically the same process,consisting of helically winding a continuous cord or cable on a form,this winding being cut circumferentially on the radially inner face ofthe form so as to be able to turn a part of the winding up around thebead wires and thus produce the carcass reinforcement with its turn-ups.

The processes described above use forms, cores or mandrels which may ormay not be rigid but are in all cases deformable since they are foldableor disassemblable, and this so that they can be withdrawn from thetoroidal reinforcement blanks. In addition to these forms or cores beingof difficult and expensive manufacture, they are also difficult to use,since they require a certain handling, which handling results in harmfuldisplacements and deformations of the sidewall and bead regions, whichareas, by definition, are the most fragile regions of the unvulcanizedtire blank.

Furthermore, these forms or cores do not in all cases assure perfectuniformity of the laying surface and, accordingly, of the shape of theproducts laid. In fact, the assembly parts of the form are assembled toeach other less and less precisely the longer the form has been used.The use of such forms thus results in a lack of uniformity on thevulcanized tire which is just as disturbing as the poor positioning ofthe products.

SUMMARY OF THE INVENTION

In order to overcome these drawbacks, and in particular to avoid anydistortion between the carcass reinforcement blank as it is on the coreand as it will be in the vulcanization mold, the process of theinvention for producing an unvulcanized toroidal tire blank consists:

a) in covering the said core with at least one layer of rubber mixintended to coat the reinforcement cords or cables;

b) producing a toroidal carcass reinforcement blank by winding acontinuous cord or cable around a non-deformable monobloc,non-disassemblable annular core or form having a meridian section theprofile of which, at least with respect to its sidewalls, is parallel tothe meridian profile of the sidewalls of the innermost carcassreinforcement ply, as it will be in the vulcanization mold;

c) laying the layers and parts of cover rubber mixes of the carcassreinforcement on said blank;

d) circumferentially cutting the carcass reinforcement blank, on the onehand, at least once on the radially inner surface and on the other handat least once on the radially outer surface of the core;

e) axially separating the two halves of the blank so as to be able toremove the building core, the separation being effected by means whichsimultaneously grasp, support and handle and have axially inner wallshaving a meridian profile identical to the meridian profile of theoutermost carcass reinforcement ply, possibly covered by the necessarylayers and parts of rubber mix, this identity being present at least inthe region of the sidewalls, as it is defined above;

f) axially bringing the said halves together and connecting them;

g) completing the tire blank before placing it in the vulcanizationmold.

By toroidal carcass reinforcement blank there is to be understood theassembly formed by the cables or cords and the so-called calenderinglayers intended to coat the cables of cords, said blank being possiblyin raw state or in prevulcanized state.

By meridian profile of the sidewalls of the carcass reinforcement plythere is understood the meridian profile of said reinforcement betweenthe points of tangency with the anchoring bead wires and the treadreinforcement respectively.

The grasping, support and handling means of the carcass reinforcementblank are preferably coaxial annular metal shells, some of theseso-called sidewall shells being intended for the support, grasping andholding of the sidewalls of the reinforcement formed on the buildingcore, said some sidewall shells being contiguous radially to the outsidewith two so-called tread shells intended for the support, grasping andhandling of the carcass reinforcement crown.

These sidewall and tread shells are provided with suction cavitieshaving valves, the cavities having rubber lips so as not to injure thecarcass reinforcement, the latter being then held within the shells byvacuum, i.e. suction.

These means are advantageously applied to the carcass reinforcementblank, built on the core, before the circumferential cuts are effected.The same is true of the placing of the anchoring bead wires of thecarcass reinforcement, which is effected by means of the sidewallshells, provided at their bases with recesses intended to receive saidbead wires, these recesses being provided on their peripheries withbead-wire holding magnets. With respect to the folding-up of the carcassreinforcement portions intended to constitute the turn-ups of saidcarcass reinforcement, it is preferably effected after the axial movingapart of the two hands of the blank and the removal of the core. To foldthe said portions of carcass reinforcement around the anchoring beadwires means that these portions, which are initially arranged axially tothe inside of the anchoring bead wires are arranged, by rotation by 180°around said bead wires, axially to the outside, while remaining parallelto the axis of rotation of the core.

As to the joining of the two halves of the blank, it can be effected bythe contribution of at least one additional reinforcement ply coveringthe two edges of the carcass reinforcement or by simple abutment of thetwo ends or by overlapping one of the two upper edges of the carcassreinforcement over the other or else by an overlapping, by at least oneply, of the edge-to-edge junction or the overlapping of both edges.

The folding of the portions of the carcass reinforcement intended toconstitute the turn-ups of said reinforcement is followed by the holdingin horizontal position of these turn-ups, this holding beingadvantageously effected either by suction or by means of suctioncavities placed below the inner faces of the sidewall shells, or, in theabsence of said shells, by the presence of two coaxial drums, the axialdistance between the axially inner faces of which may be variable.

It is advantageous, in accordance with the invention, for the laying ofthe tread reinforcement and the tread to be effected by means of aprefabricated complex formed of two elements. Likewise, the laying ofsaid complex on the crown of the carcass reinforcement blank ispreferably effected while the sidewalls of the carcass reinforcement arestill held by the so-called sidewall shells, this holding permittingperfect stability of the carcass reinforcement and of the anchoring beadwires during the course of the manufacturing process.

The same is true of the laying of the layers and parts of rubber mixesintended to form the inside of the tire, the layers and/or partsarranged axially and radially to the inside of the calendered carcassreinforcement, this laying being preferably effected while the sidewallshells are held in place on the carcass reinforcement.

DESCRIPTION OF DRAWINGS

The invention will be better understood from the accompanying drawingwhich shows non-limitative embodiments, in which drawing:

FIG. 1 shows a first variant of the blank of the carcass reinforcementas seen in meridian section in the vulcanization mold;

FIG. 2 shows the carcass reinforcement blank of FIG. 1, seen in meridiansection on the building core;

FIG. 3 shows the carcass reinforcement blank of FIG. 2 on whichgrasping, handling and support means have been placed;

FIG. 4 shows the carcass reinforcement blank after connection of theupper parts of said reinforcement and the laying of the complexconsisting of the tread reinforcement and tread;

FIG. 5 shows the finished tire blank before placing in the vulcanizationmold;

FIG. 6 shows a second variant of the carcass reinforcement blank onwhich the sidewall grasping, handling and supporting means are placed.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows a meridian cross section through the carcass reinforcement1 of a tire which is to be manufactured, this meridian section beingseen in the vulcanization mold of the tire. The carcass reinforcement 1is formed of two parts which overlap at the level of the equatorialplane XX' of the tire along an overlap width λ. The meridian profile ofthe reinforcement 1 can be broken down into three fundamental parts: amedian part AB of small transverse curvature, in which the meridianprofiles of the carcass reinforcement 1 and of the tread reinforcement(not shown) respectively are parallel to each other, the points A and Bbeing precisely the points of tangency of the meridian profile of thecarcass reinforcement with the meridian profile of the treadreinforcement. From points A and B to the points of tangency T1 and T2of the reinforcement 1 with the assemblies formed of the bead wires 2which anchor said reinforcement 1 and of the layers 3 of vulcanizedrubber mix arranged around the bead wires 2 so that the meridiansections of the assemblies are substantially circular, the carcassreinforcement has a meridian profile which is specific to it and thetransverse curvature of which, which is definitely larger, correspondsto the sidewalls of the tire.

This carcass reinforcement 1 is turned up in each bead around theassembly consisting of the bead wire 2 and the coating 3 so as to formthe turn-ups 10. The bead wires 2 will be separated in the vulcanizationmold by an axial distance referred to as "inter-bead wire" ET and thecurvilinear length between the point T₁ and the end of the turn-up 10 is1.

FIG. 2 shows the core N necessary in order to manufacture the toroidalblank of the carcass reinforcement 1 such as described above. This coreN is a closed metallic hollow torus the thickness of the wall of thetorus being such that it is practically non-deformable. The outermeridian profile of the core N, which is advantageously covered by alayer of non-sticking fabric, is, taking into account the thickness ofthe fabric and the thickness of the layer of rubber mix 4' covering thecables of the carcass reinforcement 1 on the inside and laid on saidcore, parallel to the meridian profile of said reinforcement, such asshown in FIG. 1, from the radially upper face of the core N to thepoints of tangency T₁, T₂ of the bead wires with the reinforcement, thetwo points T₁ and T₂ being then axially spaced apart by the amount Lequal to ET+2λ. The carcass reinforcement blank 1 is obtained by windinga cord or cable around the covered core N, the core resting on supportand rotation rollers, while a cord or cable distributing device permitsthe feeding of the cable and its winding around the core which turns ata given speed. Such a winding process and the device for the carryingout thereof are known and reference may be had, for instance, to Frenchpatent 2 052 885.

As shown in FIG. 3, the toroidal carcass reinforcement blank 1 iscovered with a layer of rubber mix 4" intended to cover the outside ofthe cables of said reinforcement 1, shaped parts of rubber mix 4 whichare normally located between the carcass reinforcement 1 and the treadreinforcement as well as the different layers of rubber reinforcing mix.

The toroidal blank which is covered in this manner is then clampedagainst the core N in its sidewall parts and in its tread part, with theexception of the width 2λ around the equatorial plane YY' (FIG. 2) bytwo metallic sidewall primary circular shells C_(F1) and C_(F2), saidshells being connected radially to two secondary sidewall circularshells C'_(F1) and C'_(F2), the latter being in their turn connected totwo tread circular shells C_(S1) and C_(S2), also of metal.

The connecting line of the shells C_(F1) and C'_(F1) and C_(F2) andC'_(F2) respectively is located radially substantially at a distance hfrom the imaginary line axially connecting the points of tangency T₁,T₂, h being substantially equal to 0.75 H, and H being the height of thetoroidal carcass blank 1 measured from the same imaginary limit T₁, T₂.The upper connecting line of the shells C'_(F1) and C_(S1) and C'_(F2)and C_(S2) respectively is substantially parallel to the axis of thebuilding core N and located at a radial distance from said axissubstantially equal to the radial distance between the point A and B, ofthe carcass reinforcement 1 of the tire in the mold, from the axis ofrotation of said mold.

These sidewall shells C_(F1), C_(F2), C'_(F1) and C'_(F2) and thesetread shells C_(S1), C_(S2) have axially inner faces the meridianprofiles of which correspond precisely to the meridian profile of thecarcass reinforcement blank 1 covered with the various layers of rubbermixes. The sidewall shells C_(F1) and C_(F2) are provided at theiraxially and radially inner ends with circular cavities intended toreceive the assemblies consisting of bead wires 2 and rubber coatings 3,these assemblies being placed in contact with the carcass reinforcement1 laid on the core N upon the axial displacement of the shells C_(F1),C_(F2) towards the core N.

The carcass reinforcement 1, in unvulcanized condition in the exampledescribed, and the bead-wire assemblies being held strongly in place,the carcass reinforcement 1 is cut by rotary knives D on the one hand onthe radially upper face at the place of the equatorial plane YY' of thecore and on the other hand on the radially inner face of the core at twopoints R and S such that the distances T₁ R and T₂ S are equal to thecurvilinear length 1 measured on the vulcanized tire, the part RS beingremoved from the core N.

The next step in the process of the invention consists then in axiallymoving away the shell assemblies C_(F1), C'_(F1), C_(S1) and C_(F2),C'_(F2), C_(S2), the axially and radially inner faces 101, 102, 103, 104of said shells being provided with suction cups 100 permitting theholding and transporting by suction of the carcass reinforcement blank1, without any change in the meridian profile of said blank. The suctioncups 100 are, as known, connected to an air pump which can create avacuum in said suction cups.

As indicated by the arrows F in FIG. 3, the parts T₁ R and T₂ S are thenturned up around the assemblies consisting of bead-wires 2 and coatings3 so as to come against the radially inner faces 101 of the sidewallshells C_(F1) and C_(F2), the turn-ups 10 being also held by suction.

The axial distance between the sidewall and tread shells havingpermitted the removal of the building core N, the inner finishing of thetire as well as that of the beads is then possible. It is thus that thedifferent layers of rubber mix generally forming the inner layers of thetire, such as the reinforcement layers, or the air-impervious layer ofmix in the tubeless tire are laid.

There are also laid the small reinforcement plies, known as cord orcable stiffeners or tongues 12, which are usually arranged axially tothe outside of the carcass reinforcement turn-ups in the finished tires,as well as all the layers of rubber 13 necessary for the forming of thebeads, arranged to the outside of the turn-up of the carcassreinforcement 1. All these layers of rubber are advantageously laid inaccordance with the technique described in French Patent 2 603 841 ofthe same applicant.

As can be noted in FIG. 3, the portions MO and OP of the carcassreinforcement blank, after being cut at O, are not held by the treadshells. These two portions, each of width λ, form, during the axialmovement together of the shells, the carcass reinforcement overlap suchas shown in FIG. 1.

The overlap being produced, the carcass reinforcement blank 1 is thenplaced under pressure p through an inflation member G fastened on a drumP_(o). This membrane G is advantageously reinforced at the top in such amanner as to have the rigidity suitable for the laying of aprefabricated assembly formed of the tread reinforcement 5 and the tread6 after the axial and radial moving apart of the two tread shells C_(S1)and C_(S2) and of the sidewall shells C'_(F1) and C'_(F2) (FIG. 4).Simultaneously with the moving away of C_(S1) and C_(S2), two inflatabledrums P₁, P₂ are brought axially onto opposite sides of the drum P_(o),the drums P₁ and P₂ having the object of holding in position theassemblies formed by the bead wires 2, their coatings 3, the turn-ups10, the reinforcements 12, and all the surrounding mixes 13, whichholding in position will be necessary for the external finishing of thesidewalls and beads of the tire after the axial moving apart of thesidewall shells C_(F1) and C_(F2). This finishing then consists inlaying the layers and parts of rubber mixes 14, 15, located in thevulcanized finished tire between the carcass reinforcement 1 and theturn-up 10, as well as the layers and parts of mixtures 7' and possibleply reinforcement 70, which are located on the sidewalls of the carcassreinforcement, the finishing being completed by the laying of the partsof the outer sidewall layers 7".

The tire blank is thus ready for vulcanization (FIG. 5).

The example described above corresponds fundamentally to a processintended for obtaining a tire the two carcass reinforcement halves ofwhich overlap in the upper part. One can, however, conceive of thedimensions of the core being imposed by the length of turn-up 1 of thecarcass reinforcement around the bead wires 2, and the building core Nwill be such that the axial distance L between the bead wires laidcorresponds, as a function of the curvatures of the lower face of thecore, to the sum of the turn-up lengths 1. It is then possible that, thetire in the vulcanization mold having an axial distance between beadwires ET greater than L, to obtain, after a single cut on the radiallyinner face of the core and a single cut on the radially outer face ofthe core, a space where the carcass reinforcement is missing. As shownin FIG. 6, the process consists then, after axial moving apart of thetwo halves of the blank and removal of the two tread shells C_(S1) andC_(S2) in laying an additional reinforcement ply 11 on and between thetwo upper edges of the carcass reinforcement 1.

This additional ply 11 can be formed of radial cords or cables, that isto say cords or cables which form an angle of 90° with thecircumferential direction, or cords or cables which are oriented at anangle of between 60° and 90° with respect to said direction.

After the laying of said ply, it is possible, as in first exampledescribed, to complete the blank by the laying of a tread reinforcementand of a tread, or of the prefabricated assembly of the two parts afterthe axial moving apart of the secondary sidewall shells C'_(F1) andC'_(F2).

I claim:
 1. A process for manufacturing a tire having a carcassreinforcement formed of at least one ply comprising helically winding acord or cable around a non-deformable, non-disassemblable annularmonobloc core having a meridian section the profile of which, in itssidewall and bead portions, is parallel to the meridian profile of theinnermost carcass ply as it is in the vulcanization mold for the tire,circumferentially cutting the at least one ply of carcass reinforcementto obtain two blank halves, separating axially the two blank halves bymoving apart coaxial metal shells having inner walls with means forgrasping, supporting and handling the carcass reinforcement in theregion of the sidewalls and which inner walls present a meridian profileof the outermost carcass reinforcement ply, the axial separationpermitting removal of the core, and displacing the two blank halvesaxially towards each other for connection after removal of the core. 2.A process according to claim 1, characterized by the fact that the twoblank halves are connected by means of axial overlapping of the upperedges of the carcass reinforcement (1) over an axial width λ.
 3. Aprocess according to claim 1, characterized by the fact that the twoblank halves are connected by means of at least one additional ply,formed of cords or cables inclined with respect to the circumferentialdirection of the blank by an angle α such that 90°≧α≧60°, and laid onand between the two upper edges of the carcass reinforcement.
 4. Aprocess according to claim 1, characterized by the fact that as support,grasping and handling means there are used coaxial annular metal shells,four of these shells, referred to as sidewall shells C_(F1), C_(F2),C'_(F1), C'_(F2) being intended for the grasping and support of thesidewalls of the torus formed on the core, two of said sidewall shellsC'_(F1) and C'_(F2) being joined radially to the outside to twoso-called tread shells C_(S1), C_(S2) intended for the grasping andsupport of the crown of the torus.
 5. A process according to claim 4,characterized by the use of shells C_(F1), C_(F2),C'_(F1),C'_(F2),C_(S1), C_(S2) provided with suction cavities (100)having valves, these cavities having rubber lips.
 6. A process accordingto claim 4, characterized by the fact that the primary sidewall shellsC_(F1), C_(F2) have their bases provided with recesses intended toreceive bead wires (2) for the anchoring of the carcass reinforcement(1), these recesses being provided with magnets for the holding of thebead wire (2).
 7. A process according to claim 6, including foldingportions of the carcass reinforcement blank around the anchoring beadwires (2) after axial moving apart of the two halves of the blank andholding the folded portions below radially inner faces (101) of thesidewall shells C_(F1), C_(F2) by vacuum by means of suction cavities(100) to complete the building of the beads by the laying ofreinforcement and/or rubber mix layers arranged radially to the insideof the foldings.
 8. A process according to claim 7, characterized by thefact that the finishing of the tire blank comprises, in chronologicalorder, the following steps:laying on the upper part of the carcassreinforcement blank a prefabricated complex comprising a treadreinforcement (5) and a tread (6), after removal of the tread shellsC_(S1), C_(S2), and the secondary sidewall shells C'_(F1), C'_(F2), andthe placing of the blank under pressure; putting cylindrical inflatableholding drums in place, below the folded portions of the reinforcementblank which are intended to form carcass reinforcement turn-ups andsurrounding reinforcement and/or rubber mix layers; axial moving apartof the sidewall shells C_(F1), C_(F2) ; finishing of the beads of thetire by the laying on the reinforcement blank rubber mixes arranged inthe tire between the carcass reinforcement and its turn-up, by completeturning-up of the folded portions; finishing of the sidewalls of thetire by the laying of layers of rubber mixes arranged in the sidewallsof the tire axially to the outside of the carcass reinforcement.
 9. Aprocess according to claims 4, characterized by the fact that thesupport, grasping and handling means are applied to the blank before theeffecting of the circumferential cuts.
 10. A process according to claim9, characterized by the fact that the application of the anchoring beadwires on the layer of cords or cables wound around the core N iseffected simultaneously with the application of the support, graspingand handling means.
 11. A process according to claim 1, includingapplication of reinforcement and/or rubber mix layers inside the carcassreinforcement and application of an impermeable inner layer of mix afterthe axial moving apart of the two halves of the carcass blank.